1. Technical Field
The present invention relates to an amphibian motor vehicle having a watertight engine room at a lower part of a vehicle body.
2. Background Art
Various amphibian motor vehicles are known. As shown in FIGS. 21 and 22 of the accompanying drawings, a typical conventional amphibian motor vehicle 1 includes a watertight vehicle body 2, front wheels 3, rear wheel 4 and a propeller (screw) 5. The wheels 3 and 4 are used to run on a ground and the propeller 5 is used to proceed on the water. The engine 6 drives the wheels 3 and 4 as well as the propeller 5. The engine 6 is placed in a lower part of the vehicle body 1. An engine room 8 which houses the engine 6 has to be cooled but it is important to insure that an engine room 8 is watertight even when the engine room 8 is cooled.
One example of the engine room is shown in Japanese Utility Model Application No. 54-140137, entitled "Engine Cooling Apparatus for Amphibian Motor Vehicles". As shown in FIG. 23, the engine room 8 is defined by walls 9 such that the engine room 8 is almost closed. The engine room 8 has ducts 10 and 11 extending upward. The engine 6 has an intake pipe 10 and an exhaust pipe 11. These pipes 10 and 11 extend upward in the ducts 12 and 13 respectively such that the pipes 10 and 11 can reach the air above the water level L when the vehicle 1 is cruising on the water. Free open ends of the pipes 10 and 11 extend substantially horizontal. This structure prevents the water from entering the engine room 8. Provided next to the engine 6 is a radiator 15 for cooling the engine 6. A pipe 14 connects the radiator 15 with the engine 6. The radiator 15 stands substantially vertical in the engine room 8. The radiator 15 radiates heat of a coolant flowing from the engine 6. The radiator 15 is not cooled by natural flow of air such as wind or convection so that it must be cooled by a fan 16 driven by the engine 6 or other elements.
The ducts 12 and 13 are designed to extend above the water level L when the vehicle is on the water. Thus, external air comes into and goes out of the engine room 8 through the ducts 12 and 13.
In a certain actual embodiment, the ducts 12 and 13 extend in the vehicle body 2, external air-introducing vent holes 17 are made in lateral walls of the vehicle body 2 (near a driver seat 7) and air-exhausting vent holes 18 are made in an upper wall of the vehicle body 2 (above the engine room 8), as shown in FIGS. 21 and 22. Therefore, the external air flows into the vent holes 17 and 18 and ducts 12 and 13 to reach and cool the radiator 15. In addition to the fan 16, there is provided an electrically driven fan (not shown) to expel hot air from the engine room 8 and/or to ventilate the engine room as desired.
Various types of arrangements for supporting the radiator 15 have been proposed in the case of ordinary vehicles. For example, Japanese Utility Model Application No. 55-165829, entitled "Radiator Supporting Structure", discloses a U-shaped bracket to support the radiator, which bracket is mounted on a vehicle body with bolts and nuts. Japanese Utility Model Application No. 60-130135, entitled "Radiator Mounting Structure", discloses box-shaped cross members secured on a front portion of a vehicle body to receive a lower tank of the radiator.
These conventional amphibian motor vehicles have following problems. To cool the radiator 15, the fan 16 should be driven all the time, but this lowers an engine output. In order to overcome this problem, cooling the radiator with air should be taken into account. Such cooling is commonly done by a radiator cooling construction used in a conventional ground-running vehicle. For instance, Japanese Utility Model Application No. 62-95940 ("Engine Room Arrangement") and Japanese Utility Model Application No. 62-74030 ("Radiator Arrangement") respectively disclose a structure for introducing the air into a radiator room and expelling the air to a rear of a vehicle. However, according to these teachings, the air passing through the radiator is guided in front of or at the back of the front wheels. Therefore, if an amount of the air to the right front wheel becomes larger or smaller than that to the left front Wheel, the front wheels may loose the balance and a vehicle may loose stability. Accordingly, if a ventilation passage structure employed in an ordinary ground-running vehicle is applied to the amphibian motor vehicle, it is important to insure that such a problem will not occur. And, of course, the radiator cooling arrangement for the ground vehicle cannot be directly applied to the amphibian vehicle since the engine room of the amphibian vehicle has to be watertight.
Further, since the engine room 8 is formed at a lower part of the vehicle body 2 and the radiator 15 stands in front of the engine 6 in the conventional amphibian motor vehicle, the location of the radiator 15 is limited to the lower part of the vehicle body 2. Therefore, it is impossible to manufacture an amphibian motor vehicle which exhibits the high on-water performance of an ordinary marine vessel.
There is another problem in applying the radiator supporting structure of the ordinary ground vehicle to the amphibian motor vehicle. The radiator 15 should be large in size in order to insure sufficient cooling. However, as the radiator 15 becomes larger, the supporting structure for the radiator 15 becomes larger. As a result of using a large supporting bracket, for example, the weight of the vehicle becomes large. The amphibian vehicle has a requirement of being lightweight. Therefore, the large supporting structure cannot be used. In addition, the conventional radiator is mounted on the supporting structure with screws. Therefore, mounting and removing the radiator is troublesome.
Moreover, since the engine room 8 is almost closed, heat of the exhaust pipe 11 raises the temperature of the engine room 8 and vehicle body 2. This may damage peripheral parts as well as the engine room 8 and the vehicle body 2.